1. Field of the Invention
The present invention relates to a printer controller, a printing system and a recording medium therefor and, in particular, it relates to a printer controller, a printing system and a recording medium which can realize minimum double printing and data assured printing, without deteriorating a performance of the printer, even if a printer incapable of transmitting a print completed signal is used and an error such as a paper jam occurs in the printer.
2. Description of the Related Art
In general, a printer controller is provided between a host which requests printing and a printer. The controller receives printing data transmitted from the host and transfers the data to the printer and controls the printer to print while monitoring the states of the printer.
In the prior art, if a printer incapable of transmitting data containing an error signal and printer state data to the controller or the host is used, when an error such as a paper shortage in a paper-cassette, a paper jam or a power failure has occurred, the controller works as below.
The controller judges whether data can be transferred by checking that power has been supplied to the printer, stops the data transfer when an printer error has been detected during transferring data and resumes the data transfer after the error has been corrected.
When an error in the printer is detected during transferring data, the controller sends a command to initialize the printer and resumes printing for each file.
When assuring the printing data, in other words, when checking whether the printing data is recoverable and not missed, a feed completion wait command, namely, a command for making the printer wait to respond to the data transfer of the next page until the printer completes feeding the printed paper, is added to the printing data.
Printing systems in the prior art pose several problems that cause abnormal printing such as data skip, page skip, character change and the like when an error has occurred in the printer and the printing is resumed after the error has been corrected. For example,
(1) When consecutive printing data is transferred after a power supply to the printer is recovered after the power supply turned off during printing, namely, after the printer becomes ready for printing after the power turned off.
(2) When consecutive printing data is transferred after a paper jam has been corrected after the jam occurred during printing.
In addition, when a command for making the printer wait until the printer completes feeding the printed paper is added, data transfer of the next page cannot be started for printing because the printer waits for a response to the transferring data of the next page until the printer completes feeding the printed paper. Thus, such a printing system in prior art as explained above poses a problem in that a decrease in performance in continual printing, as compared with normal printing, occurs because the mechanical performance of the printer cannot be fully utilized.
In order to solve the above problems, a printer controller comprising a storage means for storing printing data and a managing means for managing printed pages with the use of the storage means is disclosed in Japanese Patent Publication No. 2-217281 and No. 9-114618, wherein Japanese Patent Publication No. 2-217281 requires retransmission from a host to the controller while Japanese Patent Publication No. 9-114618 does not require the same for error recovery. According to the technique of these disclosed controllers, the number of printed pages can be managed and error recovery can be accomplished. However, the controllers require a storage means for storing printing data, thus the controllers cannot be made compact or economical.